Dental implant including plural anchoring means

ABSTRACT

A dental implant anchor includes a body portion having a first external wall portion carrying one or more circumferential projections separated by circumferential grooves and, below, a second external wall portion carrying threads. In some forms, the anchor also includes one or more longitudinally-oriented grooves on its exterior wall. The grooves extend across, and through the circumferential projections. The implant can include a head portion with a smooth external wall; a through-hole and an apical hole passing through the bottom of the implant; and internal structure for engaging a tool for inserting the implant in a passage formed in bone tissue. This internal structure can be in a top portion, or in an internal passage in the body portion of the implant. The method for forming a passage in bone tissue to receive the implant includes forming a passage having a base with a diameter suited to self-tapping of the threaded part of the implant, and, above the base, a larger-diameter section to engage frictionally the circumferential projections. A drill for forming such a passage in one step includes two such drilling portions that simultaneously form a two-diameter passage.

This application is a continuation-in-part of U.S. patent applicationSer. No. 07/001,807, filed Jan. 8, 1987, and entitled, "Dental ImplantIncluding Plural Anchoring Means."

This invention relates to dental implant anchoring means having, on itsouter wall, a plurality of anchoring means including an outer wallportion carrying circumferential or partially circumferentialprojections and an outer wall portion carrying threads. The outer wallportion also includes, in preferred embodiments, two or morelongitudinally-oriented grooves. These grooves intersect thecircumferential projections, preferably at right angles. In preferredembodiments, each of these grooves extend through all of thecircumferential projections on the outer wall portion. Preferably, thesegrooves are of sufficient width and depth to promote bone growth intothem of sufficient quantity and quality to minimize rotation of theimplant when inserted into an opening in bone tissue. Preferably, thesegrooves are about 0.25 mm to about 1.5 mm in depth and in width.

This anchoring means preferably includes a body portion and a topportion with the body portion carrying the plurality of anchoring meanson its outer wall. In these preferred embodiments, the top portion has asmooth external wall that tapers upwardly and outwardly from the bodyportion to a diameter that is slightly larger than the diameter of thebody portion. The top portion is sufficiently large in diameter toinsure that the top portion fits snugly within, and tightly seals, byfrictional forces, in the top of a passage formed in bone tissue toreceive the dental implant anchoring means. Alternatively, the topportion can be of substantially the same diameter as, or even of smallerdiameter than the body portion of the implant.

The dental implant anchoring means preferably includes, at its distalend, a through hole extending from one side of the body portion to theother to permit bone and associated tissue to grow through this opening.The distal end preferably also includes a passage at the bottom of thebody portion that extends upwardly inside the body portion a distancesufficient to permit blood and other tissue to pass upwardly, out thethrough-hole and up the longitudinally-oriented grooves, thus allowingthe anchor to seat at the bottom of the passage formed in bone tissue toreceive the implant. Preferably, this upwardly-extending passage is lessthan about one-third the length of the body portion.

The implant has an internal passage extending downwardly from the top ofthe implant, and internal means for engaging and inserting the implantinto a passage formed in bone tissue to receive the implant. Theinternal implant-engaging means permits insertion of the implant in apassage formed in the bone tissue of a subject without countersinkingthe upper surface of the bone tissue, where the top portion of theimplant fits upon insertion of the implant into such a passage. Thisinternal means is, preferably, a wrench-engaging surface. In preferredembodiments, where the body portion is joined to a top portion having anunthreaded, smooth exterior wall, the internal means for implantinsertion is inside this top portion. Alternatively, this internal meanscan be inside the body portion in an internal passage. Preferably, thetop portion has a hex nut configuration on its inner wall surfaces forreceiving a hex wrench, and has a cylindrically-shaped, smooth outerwall. Alternatively, the hex nut configuration can be within, and at ornear the base of the passage inside the body portion, or formed withinthreads on the wall of this passage.

In embodiments that include a top portion, the top portion is open, andcan be chamfered at its upper end, and is preferably axially alignedwith an internal passage in the body portion. The passage can bethreaded or unthreaded. This chamfered surface permits frictionallocking with any adaptor or other insert fitted into the opening. Thechamfered surface is preferably of sufficient size and depth to affordlateral stability to any adaptor or other insert fitted into the openingin the head portion, and forms a smooth, easily-cleaned margin withcomplementary adaptors placed in the top portion of the implant.

The anchoring means is preferably made of titanium or a titanium alloycontaining 6% by weight of aluminum and 4% by weight of vanadium;preferably has an outside thread diameter in the range of about 3 toabout 4.25 millimeters; an inside thread diameter in the range of about2.25 to about 3.5 millimeters; and preferably has projections with anoutside diameter that is substantially the same as, or about 0.25millimeter larger than the thread diameter. The anchoring meanspreferably has a length in the range of about 5 to 20 millimeters.

The implant anchors of this invention are adapted for insertion inspecially-formed passages in bone tissue. Preferably, the method offorming such a passage includes forming a passage in the bone tissuehaving an upper portion with a length and a diameter suitable forengaging the flutes or circumferential projections on the anchor byfriction, and including, at the base of the passage, a smaller-diameterportion adapted to engage the self-tapping threads at the bottom of theimplant. The smaller-diameter portion at the base of the opening can beformed using a first drill having a cross-section appropriate to form apassage of this diameter and with length that is about the same as thelength of the implant to be inserted. Thereafter, the upper portion ofthe passage can be enlarged by a drill of appropriate diameter toaccommodate the fluted part of the body portion of the implant.Alternatively, the smaller diameter and larger diameter portions of thepassage can be formed simultaneously using a drill having, at its end, aportion of a diameter appropriate for forming the smaller diameterportion of the passage, and an upper portion of larger diameter suitablefor forming the upper portion of the passage. The implant anchor istapped into the passage so formed until the bottom of the threadedportion reaches the top of the portion of smaller diameter at the baseof the passage. Then, using an insertion tool to engage thewrench-engaging surface inside the implant, the implant can be screwedinto the smaller-diameter part of the passage until the threaded part ofthe implant reaches the bottom of the passage.

This invention can better be understood by reference to the drawings, inwhich:

FIG. 1 is a perspective view of a first embodiment of the new dentalimplant anchor;

FIG. 2 is a perspective view of a second embodiment of the new dentalimplant anchor;

FIGS. 3A-3E show the preferred five-step method for inserting the newdental implant anchors in the bone tissue of a subject;

FIG. 4 shows an elevational view, in cross-section, of a thirdembodiment of a new dental implant anchor;

FIGS. 5 and 6 show fourth and fifth embodiments of the new dentalimplant anchoring means;

FIG. 5A is a top plan cross-sectional view, taken on line 5A--5A in FIG.5, showing the width of the longitudinal grooves on the exterior wall ofthe fourth embodiment shown in FIG. 5;

FIG. 5B is a longitudinal cross-sectional view, taken on line 5B--5B ofFIG. 5, showing the depth of the longitudinal grooves shown in FIG. 5A;

FIG. 7 shows a perspective view of a new spade drill adapted for formingan opening in bone tissue for receiving the dental implant anchors ofthis invention; and

FIG. 8 shows penetration of the drill of FIG. 7 into bone tissue to formsuch an opening.

FIG. 1 shows a first embodiment of the new dental implant anchorgenerally designated 10. Anchor 10 includes body portion 11 joined to,and surmounted by top portion 12. Body portion 11 includescircumferential projection 16, called a flute, spaced from top portion12 by circumferential groove 20 on body portion 11. Below flute 16 onbody portion 11 are threads 15. At the bottom of body portion 11 isthrough-hole 14 which passes axially through body portion 11, and apicalhole 13, formed at the bottom of implant 10, and extending upwardlyinside body portion 11 beyond through-hole 14.

Top portion 12 is joined to, and surmounts body portion 11. Top portion12 has a sidewall 17 that tapers upwardly and outwardly from the plane,near groove 20, where body portion 11 joins top portion 12.

Atop top portion 12 is opening 19 with wrench-engaging surface 18 on theinner wall of top portion 12. This wrench-engaging surface 18 permitsthreading of implant 10 into a passage formed in bone tissue by means ofa tool that fits inside implant 10, obviating the need for any insertiontool-engaging means on the outside surface of implant 10. Opening 19can, in some embodiments, be in registration with a shaft formed insidebody portion 11, and the wrench-engaging surface 18 can, in suchembodiments, be at or near the base of the shaft internal to implant 10.

FIG. 2 shows a second embodiment of the new implant, generallydesignated 32, that includes head portion 30 and body portion 31. Bodyportion 31 includes an external wall portion carrying a plurality ofcircumferential projections 33, 34, 35, 36, 37, 38 and 39. Theseprojections are in planes parallel to one another and are separated fromone another by grooves 40, 41, 42, 43, 44 and 45. Below circumferentialflutes 33-39 is another wall portion carrying threads 46. The flutesfacilitate seating the implant frictionally in a passage formed in bonetissue by tapping the implant into such a passage. Threads 46 at thebottom of body portion 31 permit the implant to be screwed into thebottom of such a passage. Thus, the implant can be held in place in sucha passage by both the flutes and the threads, or by either one alone ifthe other fails. Implant 32 also includes through hole 47 and apicalopening 48 which correspond to, and perform the same functions asopenings 13 and 14, respectively, in FIG. 1.

Top portion 30 includes opening 50 and wrench-engaging surface 51, whichare identical to, and function the same as opening 19 in wrench-engagingsurface 18, respectively, in FIG. 1. As in FIG. 1, the opening 50 may bein registration with a shaft internal to body portion 31, and thewrench-engaging surface 51 can lie inside the shaft instead of insidehead portion 30.

FIG. 4 shows a third embodiment of the new dental implant anchoringmeans. In most respects, this implant is identical to the implant shownin FIG. 1, except that the internal wrench-engaging surface 19' lies atthe bottom of the internal passage inside the implant instead of on theinternal surfaces of the top portion of the implant. While FIG. 4 showsthe internal passage, below the top portion, to be partially threaded toreceive and engage with threaded or unthreaded inserts such as dentalprostheses, the threading is not mandatory, and the walls of theinternal passage can, in alternative embodiments, be smooth instead ofthreaded, or partly threaded or partly smooth.

FIGS. 3A-3E show the preferred five-step method for inserting the newimplants into bone tissue. FIG. 3A shows the formation of a pilotpassage 60 in bone tissue 61 using a small-diameter pilot drill 62, saya drill having a diameter of about 2 millimeters. FIG. 3B shows using aspade drill 63 of slightly larger diameter than the pilot drill 62, saya diameter of 2.5 millimeters, to form a passage 64 in bone tissue 60having a length substantially the same as the length of the implant tobe inserted, and a diameter substantially the same as the diameter ofthe threaded, lower portion of the implant. FIG. 3C shows using a spadedrill 65 of slightly larger diameter than the first spade drill 63, sayapproximately 3.2 millimeters, to enlarge the upper portion of thepassage 64 formed in bone tissue in FIG. 3B to a diameter substantiallythe same as the diameter of the projections or flutes on the outer wallof the body portion above the threaded portion on the same wall. FIG. 3Dshows inserting implant 66 into the passage formed in FIG. 3C by tappingimplant 66 downwardly until the bottom of implant 66 reaches the top ofsmaller-diameter portion 67 of passage 64. FIG. 3E shows the final stepof inserting implant 66 into passage 64 formed in bone tissue byratcheting self-tapping threads 68 at the bottom of implant 66 intosmaller diameter portion 69 of passage 64 formed in bone tissue 60.

FIGS. 5 and 6 show fourth and fifth embodiments of the new dentalimplant anchoring means. In most respects, the implants of FIGS. 5 and 6are identical to those shown in FIGS. 2 and 4. However, the outer wallsurfaces 100 (FIG. 5) and 101 (FIG. 6) of each of these implants 102 and103 has two longitudinally-extending grooves 105/106 (FIG. 5) and107/108 (FIG. 6) that are diametrically disposed on opposite sides ofthe other wall and that extend from just below the base of the topportion entirely through the circumferential projections from top tobottom. These grooves interrupt, and extend across and through thesecircumferential projections on each side of the implant. These groovesare of sufficient depth and width, here about 0.25 mm to about 1.5 mm indepth (see FIG. 5B) and in width (see FIG. 5A), to insure that bonetissue will grow into these grooves enhancing the anchoring of theimplants to the bone tissue.

FIG. 7 shows a spade drill 110 having a first portion 111 and a secondportion 112. Spade drill 110 is adapted to form a generallycylindrically-shaped passage in bone tissue with a portion having afirst diameter and a portion having a second larger diameter. The firstpassage portion, of smaller diameter, is formed by first drill portion111; the second passage portion, of larger diameter, is formed by seconddrill portion 112. Spade drill 110 is adapted to form such acylindrical-shaped passage in bone tissue with two portions of differingdiameters in a single drilling operation. See FIG. 7, where drill 110penetrates into bone tissue 113 under power provided by a drillingapparatus (not shown) attached to stem 114 of drill 110. Drill 110 alsoincludes a spade-shaped portion 115 which tends to push bone tissueupwardly toward the crest of bone 116 as drill 110 penetrates bone 116(see FIG. 7).

The implants of this invention have several advantages. First, therounded flutes provide a surface adapted to receive coatings of materialsuch as hydroxyl apatite or other bone substitute materials. The flutesalso provide irregular surfaces for better distribution of stresses onthe implant from dental prostheses attached thereto. The openings andthe longitudinally-oriented grooves permit blood and other tissue at thebottom of a passage formed in bone tissue to receive these implants topass upwardly so that the implants can seat fully at the bottom of sucha passage. The upwardly, outwardly tapered head portion insures that theimplant, when inserted in a passage formed in bone tissue of sufficientdepth to receive the entire implant, seats firmly and snugly at themouth of the passage.

What is claimed is:
 1. A substantially cylindrical dental implantanchoring means comprising a substantially cylindrical body portionadapted to fit in a passage formed in jawbone tissue, said body portionhaving an external wall portion carrying at least two circumferential orpartially circumferential projections, each of said projections having asize and shape adapted to engage the walls of said passage substantiallyexclusively frictionally, each of said projections having across-section sufficiently large to engage frictionally the sidewalls ofsaid passage, and to hold said anchoring means inside said passageimmediately upon insertion of said dental implant anchoring means intosaid passage, each of said circumferential projections having a grooveon each side of the projection to facilitate growth of bone tissue intosaid grooves to promote anchoring of said dental implant in saidpassage, and, below at least said two projections, an external wallportion carrying thread means adapted to screw into the end of saidpassage, said thread means having its axis at an oblique angle to thelongitudinal axis of said substantially cylindrical dental implant;saidanchoring means further comprising: at least twolongitudinally-extending grooves passing through and interrupting eachof said circumferential projections, each of said grooves being ofsufficient depth and width to ensure bone growth into said grooves whensaid anchoring means is seated inside said passage.
 2. The dentalimplant anchoring means of claim 1 further comprising, above said bodyportion, a top portion having a smooth external wall, said top portionslanting outwardly and upwardly from a plane through said portion wheresaid body portion joins said top portion.
 3. The dental implantanchoring means of claim 2 further comprising means internal to saidimplant for engaging means for inserting said implant in said passage.4. The dental implant anchoring means of claim 3 further comprising athrough-hole passing laterally through said body portion near the bottomof said body portion.
 5. The dental implant anchoring means of claim 3wherein said implant includes two of said longitudinally-extendinggrooves, each of said grooves intersecting said circumferentialprojections at substantially right angles, each of said two grooveslying on opposite sides of the circumference of said external wallportion.
 6. The dental implant anchoring means of claim 3 wherein eachof said projections has its circumferential axis substantially normal tothe longitudinal axis of said substantially cylindrical dental implant.7. The dental implant anchoring means of claim 4 further comprising anapical hole in the body portion of said implant extending upwardlyinside said body portion beyond said through-hole.
 8. The dental implantanchoring means of claim 4 wherein said implant includes two of saidlongitudinally-extending grooves, each of said grooves intersecting saidcircumferential projections at substantially right angles, each of saidtwo grooves lying on opposite sides of the circumference of saidexternal wall portion.
 9. The dental implant anchoring means of claim 4wherein each of said projections has its circumferential axissubstantially normal to the longitudinal axis of said substantiallycylindrical dental implant.
 10. The dental implant anchoring means ofclaim 7 wherein said plant includes two of said longitudinally-extendinggrooves, each of said grooves intersecting said circumferentialprojections at substantially right angles, each of said two grooveslying on opposite sides of the circumference of said external wallportion.
 11. The dental implant anchoring means of claim 7 wherein eachof said projections has its circumferential axis substantially normal tothe longitudinal axis of said substantially cylindrical dental implant.12. The dental implant anchoring means of claim 2 wherein said implantincludes two of said longitudinally-extending grooves, each of saidgrooves intersecting said circumferential projections at substantiallyright angles, each of said two grooves lying on opposite sides of thecircumference of said external wall portion.
 13. The dental implantanchoring means of claim 2 wherein each of said projections has itscircumferential axis substantially normal to the longitudinal axis ofsaid substantially cylindrical dental implant.
 14. The dental implantanchoring means of claim 1 wherein said implant includes two of saidlongitudinally-extending grooves, each of said grooves intersecting saidcircumferential projections at substantially right angles, each of saidtwo grooves lying on opposite sides of the circumference of saidexternal wall portion.
 15. The dental implant anchoring means of claim14 wherein each of said projections has its circumferential axissubstantially normal to the longitudinal axis of said substantiallycylindrical dental implant.
 16. The dental implant anchoring means ofclaim 1 wherein each of said projections has its cirucmferential axissubstantially normal to the longitudinal axis of said substantiallycylindrical dental implant.
 17. A method for inserting a dental implantincluding plural anchoring means in a passage formed in jawbone tissueto receive said dental implant anchoring means comprising forming apassage in bone tissue having a bottom portion of a first diameter and,atop said bottom portion, a second portion having a larger diameter;inserting into said passage a dental implant anchoring means comprisinga body portion adapted to fit in a passage formed in bone tissue, saidbone portion having an external wall portion carrying at least twoprojections, each of said projections having a size and shape adapted toengage the walls of said passage substantially exclusively frictionally,at least two longitudinally-extending grooves passing through andinterrupting each of said circumferential projections, each of saidgrooves being of sufficient depth and width to ensure bone growth intosaid grooves when said anchoring means is seated inside said passage,said projections having a cross-section sufficiently large to engagefrictionally the sidewalls of said passage, and to hold said anchoringmeans inside said passage immediately upon insertion of said dentalimplant anchoring means into said passage, and, below at least said oneprojection, an external wall portion carrying thread means adapted toscrew into the end of said passage, said thread means having its axis atan oblique angle to the longitudinal axis of said substantiallycylindrical dental implant, and tapping said implant anchoring meansinto said passage sufficiently far that said external wall portioncarrying thread means reaches the top of the portion of the passagehaving said first diameter; and then screwing said dental implantanchoring means into said passage until said external wall portioncarrying threads is threaded into the smaller diameter portion of saidpassage.
 18. The method of claim 17 further comprising forming saidpassage in two steps, utilizing two separate passage-forming means, thefirst of said passage-forming means having a diameter appropriate forforming the bottom portion of the passage, and the second having alarger diameter appropriate for forming the upper portion of saidpassage.